A Malaysia airlines flight with 239 people onboard, including four Americans has gone missing. At this hour, a desperate search is under way for mh flight 370 which departed Kuala lumur at 12:41 local time. It was due to land in beijing at 6:30 A.M. Air traffic control lost contact with the plane two hours after takeoff. Whether it's due to mechanical problems, pilot error or terrorism is yet to be determined. Gloria Rivera is at the beijing airport with the latest. Cynthia, it was more than four hours before officials announced anyone awaiting word on flight 370 should head back to beijing to meet with representatives from Malaysia airlines. We saw many Chinese police here dispatched to keep control, as so many wanted answers when they were none. The Boeing 777 aircraft, similar to the one pictured here was carrying 239 people. From Malaysia's capital to beijing. Radar contact with the plane was lost in Vietnamese air space. The airline confirms four Americans onboard, one of them a child. In total there were 14 different nationality on the flight. As the day wore on, families in tears, lacking information. The beijing bound flight departed Kuala Lumpur was scheduled to land in beijing at 2:30 A.M. It was listed as delayed. We have every reason to expect this is not going to be a good outcome. A big airplane like this, losing radar contact, it usually ends up in tragedy. It was over water most of the trip. There was a it went down in the water which would make recovery that much harder. The airlines saying quote, we have deeply regret we have lost all contact with flight mh 3 70. This type of jet, the Boeing 777 has a nearly spotless safety record since it began flying in 1995. Though last summer, it was an asian airlines Boeing 777 that crashed while landing in San Francisco, killing three passengers. For"nightline," Gloria Rivera, ABC news, beijing. Our thanks to Gloria Rivera. Because flight 37was a Boeing aircraft, it is likely that American aviation authorities and the manufacturer will be involved in some way in the investigation. Going forward. ABC news will of course stay on this developing story and keep you updated with all the latest.

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